lkml.org 
[lkml]   [2014]   [Dec]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 1/3] mm: page_isolation: remove redundant moving for isolated buddy pages
On 12/09/2014 08:50 AM, Weijie Yang wrote:
> The commit ad53f92e(fix incorrect isolation behavior by rechecking migratetype)
> patch series describe the race between page isolation and alloc/free path, and
> fix the race.
>
> Now, after the pageblock has been isolated, free buddy pages are already in
> the free_list[MIGRATE_ISOLATE] and will not be allocated for usage. So the
> current freepage_migratetype check is unnecessary and it will cause redundant
> page move. That is to say, even if the buddy page's migratetype is not
> MIGRATE_ISOLATE, the page is in free_list[MIGRATE_ISOLATE], we just move it
> from free_list[MIGRATE_ISOLATE] to free_list[MIGRATE_ISOLATE].
>
> This patch removes the unnecessary freepage_migratetype check and the
> redundant page moving.
>
> Signed-off-by: Weijie Yang <weijie.yang@samsung.com>

With great hope that Joonsoo won't find another corner case J

Acked-by: Vlastimil Babka <vbabka@suse.cz>

> ---
> mm/page_isolation.c | 17 +----------------
> 1 file changed, 1 insertion(+), 16 deletions(-)
>
> diff --git a/mm/page_isolation.c b/mm/page_isolation.c
> index c8778f7..6e5174d 100644
> --- a/mm/page_isolation.c
> +++ b/mm/page_isolation.c
> @@ -221,23 +221,8 @@ __test_page_isolated_in_pageblock(unsigned long pfn, unsigned long end_pfn,
> continue;
> }
> page = pfn_to_page(pfn);
> - if (PageBuddy(page)) {
> - /*
> - * If race between isolatation and allocation happens,
> - * some free pages could be in MIGRATE_MOVABLE list
> - * although pageblock's migratation type of the page
> - * is MIGRATE_ISOLATE. Catch it and move the page into
> - * MIGRATE_ISOLATE list.
> - */
> - if (get_freepage_migratetype(page) != MIGRATE_ISOLATE) {
> - struct page *end_page;
> -
> - end_page = page + (1 << page_order(page)) - 1;
> - move_freepages(page_zone(page), page, end_page,
> - MIGRATE_ISOLATE);
> - }
> + if (PageBuddy(page))
> pfn += 1 << page_order(page);
> - }
> else if (page_count(page) == 0 &&
> get_freepage_migratetype(page) == MIGRATE_ISOLATE)
> pfn += 1;
>



\
 
 \ /
  Last update: 2014-12-09 10:41    [W:0.041 / U:0.248 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site